1. Field of the Invention
The present invention relates to a digital camera for outputting image data, which is not processed, received from an image pickup unit.
2. Description of the Related Art
A digital camera enables a user to confirm an image, which will be picked up, by continuously displaying an image of an object before picking up an image. The digital camera also enables a user to confirm a picked-up image by reproducing and displaying the picked-up image immediately. Especially, the function that the digital camera reproduces a picked-up image immediately after picking up is convenient for user. In this case, the image data obtained by picking up are converted into image signal form, which is for appropriate for that an image display unit displays, and recorded on recording media. For example, a combination of luminance Y signal, color difference R-Y signal and color difference B-Y, or a combination of RGB signals are used for image signal form.
Another digital camera is proposed that can output image data, which is not processed, received from an image pickup unit having a CCD image pickup element (see JP-A-11-261933 or JP-A-2001-223979). When image data received from the image pickup unit (hereafter, it is called “RAW data” as image data, which is not processed, received from the image pickup unit.) are employed, an image signal can be obtained that reflects the pixel structure and the characteristic of the image pickup unit. Therefore, a user can perform an image correction process that does not deteriorate the image.
An example of image correction process for RAW data is a white balance (WB) control process. In the white balance control process, a gain for each color signal of RAW data is changed to obtain image data of appropriate tone of color. The digital camera has a white balance control function, which performs the white balance control process by using color gain data that are set by user before picking up an image. Image data, which the white balance control process was processed, are employed to convert to the image signal form that is appropriate for image reproduction.
A white balance can be manually set in accordance with light source condition (outdoors, shade, illumination) or also can be automatically adjusted and set (auto white balance) in accordance with the scene where is picked up. Color gain data, which is obtained in accordance with the settings, vary among cameras used for picking up even though the settings of each camera is same because of the type of CCD image pickup element and the characteristic difference of each element. Further, the auto white balance control process is performed by an algorithm in accordance with the type of camera and the characteristics of each camera.
Therefore, it is preferable to output RAW data with color gain data which were set before picking up. According to the camera disclosed in JP-A-2001-223979, color gain data for white balance, which were set before picking up, as parameter for image reproduction are added to RAW data.
An arbitrary correction process to the output RAW data can be performed by an external processor. Whereas, when a white balance control process is to be performed under various light source conditions, user may request to slightly control hue by setting each light source with a color temperature. As described above, however, since a color gain corresponding to each light source condition is varied among cameras, a first circumstance may occur to that an appropriate corrected image can not be obtained even by setting a light source condition in accordance with a color temperature.
In the case of that the color correction process to the output RAW data is performed, when a user finds that the settings in picking up an image is inappropriate, the user may want to adjust the image under different light source condition. As described above, however, since the color gain corresponding to each light source condition is varied among cameras, a second circumstance may occur to that the adjustment is in actuality difficult.
Although color gain data attached with the output RAW data are generally unclear about the settings, there is a case that an auto white balance control process is desired by using an external processor. However, even though a color gain is obtained through the analysis of a picking-up scene, as described above, a third circumstance may occur to that optimal auto white balance control is difficult due to the difference (a characteristic and a process algorithm) in individual cameras.